Many projection systems, such as digital light projectors (DLPs), utilize a white light and a color filter wheel to produce different colors. The color filter wheel, which typically includes segments for each of the primary colors red, blue, and green, spins at a predetermined rate as the white light is projected onto the color filter wheel. As the white light passes through the color filter wheel, only certain wavelengths are allowed to pass through the various segments of the color filter wheel, thereby producing colored lights corresponding to the colors of the color filter wheel. An integrator receives the colored light and projects the colored light toward a viewing surface. Lenses and/or mirrors may be added as necessary to focus the light.
When the distinct colors of the color filter wheel are projected onto the viewing surface at a fast rate, the human eye integrates the color to form other colors, such as combining blue and red to form purple. Various colors and shades may be formed by altering the amount of light (length of time) each color is projected.
Because the colors are projected individually and the human eye integrates the different colors to form other colors, the displayed image may contain certain artifacts. One such artifact is referred to as the rainbow effect. This effect is typically seen along the edges of an object when the viewer moves or sweeps their eyes across the viewing angle. In these instances, some viewers are able to see the separate colors of the color wheel along the edges, which appear similar to a rainbow along the edges. When using a red, blue, and green color filter wheel, the rainbow primarily consists of red and green colors—the darker blue color is not observed as often.
One attempt to solve this problem involved spinning the color filter wheel at a higher rate. For example, to produce an image at a 60 Hz rate, the color filter wheel may be spun at a 120 or 240 Hz rate. It has been found that spinning the color filter wheel at a higher rate allows more samples of the various colors to be produced within a given period of time. The color bands are now smaller and are more difficult for the human eye to separate the individual colors.
Spinning the color filter wheel at a higher rate, however, may cause problems. For example, the higher the spin rate, the more difficult it may be to control the electrical and mechanical operations of the projection system. Therefore, there is a need for a system and method for using sequential color techniques in a projection system that may reduce the rainbow effect.